1. Field of the Invention
This invention pertains to an expandable internal holding chuck.
2. The Prior Art
Prior art internal chucking devices are typically of an expanding wedge, internal cam, i.e. a hexagonal internal cam and six, radial expanding followers that the hexagonal cam forces outwards, or of some other multi-jaw structure. These devices usually have many mechanical components and as a result thereof have many crevices exposed to the exterior and open to dirt, chemicals, dust, debris and the like when in use. The prior art chucks when used on horizonal axis equipment, examples of which are tension or drive shafts for rolls of paper, steel and other bulk rolled sheet material, are typically characterized by not being able to concentrically chuck a heavy roll suspended on the chuck. The reason for this characteristic is that because of the tremendous roll weight, the roll drops upon the top of the chuck and when the chuck is tightened up, the top teeth or cams in the chuck are firmly engaged by the roll and what were the bottom teeth or cams are loose. These teeth or cams are also referred to as jaws in the trade. After tightening of the just described prior art chucks, when the roll is turned about the axis of the chuck, the roll runs eccentrically.
Further, because of the complexity of prior art chucks, maintenance is considered to be a considerable problem, particularly in the paper industry.
Another disadvantage, or limiting factor may be more appropriate, is that an increased contact area between the chuck and the item being chucked has been desired in order to preclude the chuck from turning in or distorting the inside of the item being chucked.